ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Volume 35,Issue 2,2009 Table of Contents
Zhen Yuanyuan
,
Zhang Xiaoling
,
Zhu Hongfang
,
Ye Jinyin
,
Fang Xiang
,
Zhang Jiao
,
Zhang Xuechen
,
Yuan Song
,
Shi Shuaihong
2009, 35(2):3-7.
DOI: 10.7519/j.issn.1000-0526.2009.2.001
Abstract:
By using the data of radar and satellite, lightning positioning a nd NCEP data, the mesoscale characteristics of the excessive storm occurring in the western region along Huaihe in Anhui on July 8th，2007 were analyzed. The re sults show that the big convective echo band producing the excessive storm was c onsistent with the convergence area at 925hPa. The convective cell moved in the same direction as echo band, but the mesoscale rainstorms pro pagated backwards. It moved in the oppositional direction with the single cell w hich made the big echo relatively stable in a specific area and caused the exces sive storm. The maximum hourly precipitation almost appeared when intense convec tion and convective echo merging. Furthermore by analyzing the twodimension al wind field retrieved of single Doppler radar, the cyclonic shear maintaining at low and middle level was the important condition which caused and maintained the severe rainfall.
By using the data of radar and satellite, lightning positioning a nd NCEP data, the mesoscale characteristics of the excessive storm occurring in the western region along Huaihe in Anhui on July 8th，2007 were analyzed. The re sults show that the big convective echo band producing the excessive storm was c onsistent with the convergence area at 925hPa. The convective cell moved in the same direction as echo band, but the mesoscale rainstorms pro pagated backwards. It moved in the oppositional direction with the single cell w hich made the big echo relatively stable in a specific area and caused the exces sive storm. The maximum hourly precipitation almost appeared when intense convec tion and convective echo merging. Furthermore by analyzing the twodimension al wind field retrieved of single Doppler radar, the cyclonic shear maintaining at low and middle level was the important condition which caused and maintained the severe rainfall.
2009, 35(2):8-14.
DOI: 10.7519/j.issn.1000-0526.2009.2.002
Abstract:
MM5 through using various cumulus parameterization schemes and various leading times from both deterministic and ensemble forecast points of view. The results show that the simulated tracks with 48h leading tim e at 1200 UTC on 7 Aug. 2005 with various cumulus parameterization schemes all t urn to the northeast and consequently will not have a direct impact on Beijing. When the leading time extends to 60 and 72 hours, the simulated tracks with the predictability of the recurvature of typhoon Matsa (0509) in Bohai on August 9, 2005 was examined with Kuo and BettsMiller cumulus parameterization schemes ar e still close to the observations, while the simulated storms with Grell and KainFritch schemes deviate to the n orthwest of the real track and thus may affect Beijing directly. The better per formance of Kuo and BettsMiller schemes in predicting the sudden turning of Ma tsa in Bohai is also confirmed in the ensemble forecast. An uncertainty of forec ast with Kuo and BettsMiller cumulus parameterization schemes was observed to be smaller than that with Grell and KainFritch schemes. The predictability of Ma tsa sudden turning to the northeast at Bohai could be around 2 days.
MM5 through using various cumulus parameterization schemes and various leading times from both deterministic and ensemble forecast points of view. The results show that the simulated tracks with 48h leading tim e at 1200 UTC on 7 Aug. 2005 with various cumulus parameterization schemes all t urn to the northeast and consequently will not have a direct impact on Beijing. When the leading time extends to 60 and 72 hours, the simulated tracks with the predictability of the recurvature of typhoon Matsa (0509) in Bohai on August 9, 2005 was examined with Kuo and BettsMiller cumulus parameterization schemes ar e still close to the observations, while the simulated storms with Grell and KainFritch schemes deviate to the n orthwest of the real track and thus may affect Beijing directly. The better per formance of Kuo and BettsMiller schemes in predicting the sudden turning of Ma tsa in Bohai is also confirmed in the ensemble forecast. An uncertainty of forec ast with Kuo and BettsMiller cumulus parameterization schemes was observed to be smaller than that with Grell and KainFritch schemes. The predictability of Ma tsa sudden turning to the northeast at Bohai could be around 2 days.
2009, 35(2):15-18.
DOI: 10.7519/j.issn.1000-0526.2009.2.003
Abstract:
Aiming at the two heavy rainfalls over Jianghuai area on 14 July, 2007 , and 16 August, 2008, the cloud liquid water path retrieved from the visible, i nfrared and nearinfrared data of FY-2C satellite is compared with the precipi ta tion data of the same period. The results show that when the cloud liquid water path maintains large value, strong precipitation occurs on the surface. There ex ists a positive relationship between the precipitation and the cloud liquid wate r path. It indicates that the cloud characteristic parameters product is usab le in the precipitation analysis.
Aiming at the two heavy rainfalls over Jianghuai area on 14 July, 2007 , and 16 August, 2008, the cloud liquid water path retrieved from the visible, i nfrared and nearinfrared data of FY-2C satellite is compared with the precipi ta tion data of the same period. The results show that when the cloud liquid water path maintains large value, strong precipitation occurs on the surface. There ex ists a positive relationship between the precipitation and the cloud liquid wate r path. It indicates that the cloud characteristic parameters product is usab le in the precipitation analysis.
2009, 35(2):19-28.
DOI: 10.7519/j.issn.1000-0526.2009.2.004
Abstract:
In order to study the formation mechanism of urban heavy fog and the pollution o f fogwater, an observation of a heavy fog with the visibility of 100m during 1 1-12 Dec, 2006 was made in Beijing Observatory located in the south suburb (39° 56′N，116°17′E). The synoptic system and fogwater ionic species concentrati on was analyzed in the work. The results demonstrated that the observed fog proc ess was an advectionradiation fog with a deep layer of more than 150 meters and a low visibility of less than 100 meters. In the front of upper t rough there exits a stable boundary layer, accompanying with convergence and wa rm moist advection in the surface positive relative vorticity area. The surface temperature decreased rapidly after sunset, which is favorable for the fog f ormation. The southoriented wind and warm advection layer on the ground result in an increase of fog concentration. The formation and increase of heavy fog acc ompany with the air pollution index Ⅴ(APIⅤ) increasing. Compared with Beijing' s fogwater sample of 1999, the pH rises, electric conductivity rate descents, t he anion’s concentration generally decreased and the cation concentration incre ased. Investigation shows that the pollution of heavy fog and fogwater of Beij ing has been reduced through efficient control.
In order to study the formation mechanism of urban heavy fog and the pollution o f fogwater, an observation of a heavy fog with the visibility of 100m during 1 1-12 Dec, 2006 was made in Beijing Observatory located in the south suburb (39° 56′N，116°17′E). The synoptic system and fogwater ionic species concentrati on was analyzed in the work. The results demonstrated that the observed fog proc ess was an advectionradiation fog with a deep layer of more than 150 meters and a low visibility of less than 100 meters. In the front of upper t rough there exits a stable boundary layer, accompanying with convergence and wa rm moist advection in the surface positive relative vorticity area. The surface temperature decreased rapidly after sunset, which is favorable for the fog f ormation. The southoriented wind and warm advection layer on the ground result in an increase of fog concentration. The formation and increase of heavy fog acc ompany with the air pollution index Ⅴ(APIⅤ) increasing. Compared with Beijing' s fogwater sample of 1999, the pH rises, electric conductivity rate descents, t he anion’s concentration generally decreased and the cation concentration incre ased. Investigation shows that the pollution of heavy fog and fogwater of Beij ing has been reduced through efficient control.
2009, 35(2):29-33.
DOI: 10.7519/j.issn.1000-0526.2009.2.005
Abstract:
By using the sounding data, surface wind vector, sounding data, NCEP d ata and the boundary convergence line detected by Jinan Doppler weather radar, s evere convective storms happened in Shandong province during 2005-2007 were anal yzed. The results show that Doppler weather radar with high spatial and time res olution can obtain the information of boundary convergence zone. Normally, the n arrow band echo reflects the existence of thunderstorm outflow and surface wind field convergence zone. The outflow boundary keeps away from storms or the con vergence zone moved in the same direction because the surface wind can't trigger convective storm in a condition of weak thermal instability. The coalescen t of two outflow boundary or the coalescent of the outflow boundary and the surf ace wind convergence zone can trigger local severeconvective storms, whereas the single surface wind convergence zone can produce isolated convective storms. The se results can afford a pivotal reference for short range forecasting and convec tive storm nowcasting. The difficulties in nowcasting convective storms are the incertitude of initial echo location, the formative time of initial echo and the type of convective storms.
By using the sounding data, surface wind vector, sounding data, NCEP d ata and the boundary convergence line detected by Jinan Doppler weather radar, s evere convective storms happened in Shandong province during 2005-2007 were anal yzed. The results show that Doppler weather radar with high spatial and time res olution can obtain the information of boundary convergence zone. Normally, the n arrow band echo reflects the existence of thunderstorm outflow and surface wind field convergence zone. The outflow boundary keeps away from storms or the con vergence zone moved in the same direction because the surface wind can't trigger convective storm in a condition of weak thermal instability. The coalescen t of two outflow boundary or the coalescent of the outflow boundary and the surf ace wind convergence zone can trigger local severeconvective storms, whereas the single surface wind convergence zone can produce isolated convective storms. The se results can afford a pivotal reference for short range forecasting and convec tive storm nowcasting. The difficulties in nowcasting convective storms are the incertitude of initial echo location, the formative time of initial echo and the type of convective storms.
2009, 35(2):34-40.
DOI: 10.7519/j.issn.1000-0526.2009.2.006
Abstract:
3 squall line weather processes in North China were selected and studied, which represent three different types of typical squall line system with trailing stra tiform (TS), leading stratiform (LS) and parallel sratiform (PS). The used data include Doppler radar, cloudtoground lightning, radiosonde and the data by v ariable width netgrids. The relationship between cloudtoground lightning f requency every 6 minutes and echo top parameter was studied by using the top hei ght of whole squall line and its upper part. The results show that cloudtogr ound lightning frequency in period of 6 minutes appeared a range above 8km are 8 5.8%, 78.9% and 80.5%, respectively for three squall processes, and they correla te positively to the areas of cloud tower height reaching above 11km or 12km (ec ho top above 11km). Especially, at part intense lightning activity range of squa ll line systems, the total areas of echo top above 11km can be used as an indica tor of lightning warning. These results are meaningful to the lightning nowcas ting and to understanding of lightning activity in squall line system in North C hina.
3 squall line weather processes in North China were selected and studied, which represent three different types of typical squall line system with trailing stra tiform (TS), leading stratiform (LS) and parallel sratiform (PS). The used data include Doppler radar, cloudtoground lightning, radiosonde and the data by v ariable width netgrids. The relationship between cloudtoground lightning f requency every 6 minutes and echo top parameter was studied by using the top hei ght of whole squall line and its upper part. The results show that cloudtogr ound lightning frequency in period of 6 minutes appeared a range above 8km are 8 5.8%, 78.9% and 80.5%, respectively for three squall processes, and they correla te positively to the areas of cloud tower height reaching above 11km or 12km (ec ho top above 11km). Especially, at part intense lightning activity range of squa ll line systems, the total areas of echo top above 11km can be used as an indica tor of lightning warning. These results are meaningful to the lightning nowcas ting and to understanding of lightning activity in squall line system in North C hina.
7 Observation Analysis on a Torrential Rain Event in Liaoning Province Trigged b y a Mesoscale Jet
2009, 35(2):41-48.
DOI: 10.7519/j.issn.1000-0526.2009.2.007
Abstract:
Based on the data of AWS, radiosonde observations, satellite and Doppler Radar D ata, an analysis on the jets in a torrential rain event in Liaoning Province on July 31, 2008 was conducted. The results show that, a large scale southerly jet and a mesoscale southwesterly jet preexisted in the boundary layer backgr ound and in the left side of latter a southwestnortheast mesoβ cloud cluste r band caused the heavy precipitation directly. The further analysis indicates tha t the mesoscale boundary layer southwesterly jet was near to the high level je t in direction and speed. The bishear pattern wind field trigged the unstable d e velopment of vortex Rossby gravity wave in the left side of the boundary jet. It gave birth to the mesoβ cloud cluster band.
Based on the data of AWS, radiosonde observations, satellite and Doppler Radar D ata, an analysis on the jets in a torrential rain event in Liaoning Province on July 31, 2008 was conducted. The results show that, a large scale southerly jet and a mesoscale southwesterly jet preexisted in the boundary layer backgr ound and in the left side of latter a southwestnortheast mesoβ cloud cluste r band caused the heavy precipitation directly. The further analysis indicates tha t the mesoscale boundary layer southwesterly jet was near to the high level je t in direction and speed. The bishear pattern wind field trigged the unstable d e velopment of vortex Rossby gravity wave in the left side of the boundary jet. It gave birth to the mesoβ cloud cluster band.
2009, 35(2):49-56.
DOI: 10.7519/j.issn.1000-0526.2009.2.008
Abstract:
Conventional observing data, FY2C satellite infrared and vapor pictures, auto station intensive surface observing data and new generation Doppler radar dete ction data were used to analyze an unusual “thunderstorm snow” weather event w hich happened from February 28 night to February 29 morning in 2008. The result indicated that the interact ion of southern trough, cold air and southwest lower jet was the beneficial sy noptic background. The strong convection weather just happened in the baroclinic instability environment of humidity front with the interaction between jet and cold front. The mesoγscale convective cloud grew and gradually strengthened to mesoβscale convective cloud which was the primary mesoscale synoptic system and triggered this complex convective weather event. From the Doppler radar ech o picture we could see that the band echo with the shape of “人” and “hail sp ike” hook echo with the echo intensity of 25～33dBz, and gust front can also be detected from the PPI screen. And from the VPPI screen, antiwind area, lower l evel’s zero isotherm “S” warm advection and “bull′s eye” structure can als o be detected, which were classical features of mesoscale convective system′s changing from weakness to strength during the period of rainfall evolving to ha il and snow in the “thunderstorm snow” weather. The fast evolving characters o f hourly surface temperature, pressure, relative humidity and wind showed the va lue of temperature, pressure and humidity increased before the thundersto rm happened, and the value of temperature and pressure got to maximum, and the p ressure curve appeared to domeshaped mesoscale thunderstorm high pressure f eature. And any other else, the evolving of wind showed the wind rotated anticlockwise, and the northern wind velocity increased and the peak value app eared. When the thunderstorm passed, the meteorological factors showed th e temperature decrensing, and the humidity increasing, and the dew poin t temperature got to peak value.
Conventional observing data, FY2C satellite infrared and vapor pictures, auto station intensive surface observing data and new generation Doppler radar dete ction data were used to analyze an unusual “thunderstorm snow” weather event w hich happened from February 28 night to February 29 morning in 2008. The result indicated that the interact ion of southern trough, cold air and southwest lower jet was the beneficial sy noptic background. The strong convection weather just happened in the baroclinic instability environment of humidity front with the interaction between jet and cold front. The mesoγscale convective cloud grew and gradually strengthened to mesoβscale convective cloud which was the primary mesoscale synoptic system and triggered this complex convective weather event. From the Doppler radar ech o picture we could see that the band echo with the shape of “人” and “hail sp ike” hook echo with the echo intensity of 25～33dBz, and gust front can also be detected from the PPI screen. And from the VPPI screen, antiwind area, lower l evel’s zero isotherm “S” warm advection and “bull′s eye” structure can als o be detected, which were classical features of mesoscale convective system′s changing from weakness to strength during the period of rainfall evolving to ha il and snow in the “thunderstorm snow” weather. The fast evolving characters o f hourly surface temperature, pressure, relative humidity and wind showed the va lue of temperature, pressure and humidity increased before the thundersto rm happened, and the value of temperature and pressure got to maximum, and the p ressure curve appeared to domeshaped mesoscale thunderstorm high pressure f eature. And any other else, the evolving of wind showed the wind rotated anticlockwise, and the northern wind velocity increased and the peak value app eared. When the thunderstorm passed, the meteorological factors showed th e temperature decrensing, and the humidity increasing, and the dew poin t temperature got to peak value.
2009, 35(2):57-63.
DOI: 10.7519/j.issn.1000-0526.2009.2.009
Abstract:
With the TBB data from FY2C satellite and the hourly observed precipitation da ta, the TBB features of torrential rain in Huaihe River valley from June 30 to Jul y 10, 2007 are studied. Based on the records of the strongest rainfall period, s ome synoptic and climatic characteristics are summarized. The results show that TBB can directly and quantitatively present the features of intensity and distributi on of cloud system with heavy rainfall. The torrential rainfall and the lower TB B band have a good relationship, and the southwest monsoon is very strong. The t ransported water vapor from the South China Sea to the northeast along the north west side of the subtropical high and Guangxi Province, and the constant flow of fresh air from westerly trough, meet in Huaihe River valley, which plays an important part in the generation, development and maintenance of the strong conv ective cloud cluster in Huaihe River valley. The lower TBB band along the Huaih e River valley is less dynamically stable with a small northsouth swing, and t he process appear to be in a cycles of developmentenhancementweakeningreg eneration, which causes in a torrential rain over Huaihe River valley.
With the TBB data from FY2C satellite and the hourly observed precipitation da ta, the TBB features of torrential rain in Huaihe River valley from June 30 to Jul y 10, 2007 are studied. Based on the records of the strongest rainfall period, s ome synoptic and climatic characteristics are summarized. The results show that TBB can directly and quantitatively present the features of intensity and distributi on of cloud system with heavy rainfall. The torrential rainfall and the lower TB B band have a good relationship, and the southwest monsoon is very strong. The t ransported water vapor from the South China Sea to the northeast along the north west side of the subtropical high and Guangxi Province, and the constant flow of fresh air from westerly trough, meet in Huaihe River valley, which plays an important part in the generation, development and maintenance of the strong conv ective cloud cluster in Huaihe River valley. The lower TBB band along the Huaih e River valley is less dynamically stable with a small northsouth swing, and t he process appear to be in a cycles of developmentenhancementweakeningreg eneration, which causes in a torrential rain over Huaihe River valley.
10 Statistical Analysis of the Thunderstorm and Convective Parameters from May to September in 2006
2009, 35(2):64-70.
DOI: 10.7519/j.issn.1000-0526.2009.2.010
Abstract:
Statistical analysis about the characteristics of the temporal and spa tial distribution of the thunderstorm from May to September in 2006 is conducted . The results are as follows: (1)The occurrence of the thunderstorm is shortra nge and lo cal. Most of them happen at 17 p.m. and 20 p.m. in the evening, while only a few at 11 a.m.; (2)The stations that once the thunderstorm happened are less then 1 /3 of all the stations. From the spatial distribution of the thunderstorm, the are a with hig h frequency of the thunderstorm focus on Guangdong, Guangxi and Yunnan province, while in the west of InnerMongloia, northern part of Xinjiang and Qinhai etc . are the area with less thund erstorm; (3)The distribution of the convective parameters present di fferent characteristics. The most important point is that, when the thunderstorm happens, there are three high frequency areas and the corresponding convective parameters centralize in a certain range.
Statistical analysis about the characteristics of the temporal and spa tial distribution of the thunderstorm from May to September in 2006 is conducted . The results are as follows: (1)The occurrence of the thunderstorm is shortra nge and lo cal. Most of them happen at 17 p.m. and 20 p.m. in the evening, while only a few at 11 a.m.; (2)The stations that once the thunderstorm happened are less then 1 /3 of all the stations. From the spatial distribution of the thunderstorm, the are a with hig h frequency of the thunderstorm focus on Guangdong, Guangxi and Yunnan province, while in the west of InnerMongloia, northern part of Xinjiang and Qinhai etc . are the area with less thund erstorm; (3)The distribution of the convective parameters present di fferent characteristics. The most important point is that, when the thunderstorm happens, there are three high frequency areas and the corresponding convective parameters centralize in a certain range.
2009, 35(2):71-79.
DOI: 10.7519/j.issn.1000-0526.2009.2.011
Abstract:
Recent studies carried out by the Hong Kong Observatory show that the rising trends of air temperature in Hong Kong are influenced by both the global warming due to enhanced greenhouse effect and the high density urban development in Hong Kong. Apart from temperature, urbanization also brings about obvious d ifferences between the urban and rural areas in respect of relative humidity. The scope of the present study includes the selection of representative urban an d rural meteorological stations in Hong Kong so that the temperature difference between those chosen urban and rural stations can be utilized to quantify the ef fect of urbanization. By making use of some 20 years’ hourly temperatures and relative humidity data, this study preliminarily compared the diurnal variations and seasonal variations of the differences in temperatures an d relative humidity between urban and rural stations, and try to analyze the rel ationship between these differences and urbanization.
Recent studies carried out by the Hong Kong Observatory show that the rising trends of air temperature in Hong Kong are influenced by both the global warming due to enhanced greenhouse effect and the high density urban development in Hong Kong. Apart from temperature, urbanization also brings about obvious d ifferences between the urban and rural areas in respect of relative humidity. The scope of the present study includes the selection of representative urban an d rural meteorological stations in Hong Kong so that the temperature difference between those chosen urban and rural stations can be utilized to quantify the ef fect of urbanization. By making use of some 20 years’ hourly temperatures and relative humidity data, this study preliminarily compared the diurnal variations and seasonal variations of the differences in temperatures an d relative humidity between urban and rural stations, and try to analyze the rel ationship between these differences and urbanization.
2009, 35(2):80-87.
DOI: 10.7519/j.issn.1000-0526.2009.2.012
Abstract:
Based on the hourly rain intensity data in 485 stations of China durin g 1991 to 2005, the SpatialTemporal distribution features of hourly rain inten sity are analyzed with probability distribution analyses and statistical test. The hourly rain intensity was divided into four levels，more than 1 mm, 2 mm, 4 mm and 8mm per hour. The hourly rain intensity distribution character in differe nt levels was analyzed for the whole year and the distribution of the maximum of hourly rain intensity. Then, the daily variation of rain intensity was investig ated. The results showed that the features of daily variation were different in different areas and obvious in the West South and the South China. Furthermore, the recurrence periods of 50, 100 years of the maximum of hourly rain intensity were estimated primarily. It seemed that their distribution trends were consiste n t. The maximum area can be found in the southeast coastal range. The maximum of hourly rain intensity in 100 years can reach 100-150 mm/h in these regions.
Based on the hourly rain intensity data in 485 stations of China durin g 1991 to 2005, the SpatialTemporal distribution features of hourly rain inten sity are analyzed with probability distribution analyses and statistical test. The hourly rain intensity was divided into four levels，more than 1 mm, 2 mm, 4 mm and 8mm per hour. The hourly rain intensity distribution character in differe nt levels was analyzed for the whole year and the distribution of the maximum of hourly rain intensity. Then, the daily variation of rain intensity was investig ated. The results showed that the features of daily variation were different in different areas and obvious in the West South and the South China. Furthermore, the recurrence periods of 50, 100 years of the maximum of hourly rain intensity were estimated primarily. It seemed that their distribution trends were consiste n t. The maximum area can be found in the southeast coastal range. The maximum of hourly rain intensity in 100 years can reach 100-150 mm/h in these regions.
2009, 35(2):88-93.
DOI: 10.7519/j.issn.1000-0526.2009.2.013
Abstract:
Lband Radar and Electrical Radiosonde System (LRERS) had been employed widely ，but the detection accuracy of Lband Radar was obtained only by check ing short distance static objects, which lacked related dynamic test. In order t o know the altimetry precision of LRERS, a new radiosonde with GPS function modu le was developed, In view of high precision GPS being generally acknowledge d in the world, 23 electrical radiosondes with GPS function model was set free w hich were traced by Lband radar in Shanghai and Nanjing from the last ten days of May to the first ten days of June,2006. It is demonstrated from the analyzed result of 23 intercomparison data that As a wind-finding equipment, the height measuring error of Lband radar is rather big because of the less ac c uracy of the horizontal calibration precision，the most system deviation is seve ral hectometers under the height of 100hPa. At the same time,it is found that t he error is systematic at a given station. However, if the radar level is adjust ed refer to the intercomparison result with GPS position data, the accuracy of t he height measurement may be improved in much more degree, which is less than 40 meters below 100hPa height. so it is feasible to use GPS position data as Calib ration reference method of Lband Radar.
Lband Radar and Electrical Radiosonde System (LRERS) had been employed widely ，but the detection accuracy of Lband Radar was obtained only by check ing short distance static objects, which lacked related dynamic test. In order t o know the altimetry precision of LRERS, a new radiosonde with GPS function modu le was developed, In view of high precision GPS being generally acknowledge d in the world, 23 electrical radiosondes with GPS function model was set free w hich were traced by Lband radar in Shanghai and Nanjing from the last ten days of May to the first ten days of June,2006. It is demonstrated from the analyzed result of 23 intercomparison data that As a wind-finding equipment, the height measuring error of Lband radar is rather big because of the less ac c uracy of the horizontal calibration precision，the most system deviation is seve ral hectometers under the height of 100hPa. At the same time,it is found that t he error is systematic at a given station. However, if the radar level is adjust ed refer to the intercomparison result with GPS position data, the accuracy of t he height measurement may be improved in much more degree, which is less than 40 meters below 100hPa height. so it is feasible to use GPS position data as Calib ration reference method of Lband Radar.
2009, 35(2):94-100.
DOI: 10.7519/j.issn.1000-0526.2009.2.014
Abstract:
In 2007, the tropical cyclone activity over the Northwest Pacific exhi bits the following features as compared to normal years: (1) the active tropical cyclone season shifts about 2 months later; (2) the area of tropical cyclogenes is is more northward and abrupt changes in latitudes of genesis occur twice in t he year; (3) the intensity of tropical cyclone as a whole is slightly weaker whi le individual one is more intense; and (4) there is a higher rate of landfall tr opical cyclones. These characteristics are associated with ENSO phenomenon which turns from El Nino to La Nina in the year. Consequently, a more favorable envir onment for tropical cyclones occurs since August, including the strengthened lar gescale ascending motions and ITCZ, the northward subtropic high, small local v ertical shear, and active turbulences in low troposphere.
In 2007, the tropical cyclone activity over the Northwest Pacific exhi bits the following features as compared to normal years: (1) the active tropical cyclone season shifts about 2 months later; (2) the area of tropical cyclogenes is is more northward and abrupt changes in latitudes of genesis occur twice in t he year; (3) the intensity of tropical cyclone as a whole is slightly weaker whi le individual one is more intense; and (4) there is a higher rate of landfall tr opical cyclones. These characteristics are associated with ENSO phenomenon which turns from El Nino to La Nina in the year. Consequently, a more favorable envir onment for tropical cyclones occurs since August, including the strengthened lar gescale ascending motions and ITCZ, the northward subtropic high, small local v ertical shear, and active turbulences in low troposphere.
2009, 35(2):101-105.
DOI: 10.7519/j.issn.1000-0526.2009.2.015
Abstract:
Positioning and forecast errors of tropical cyclones over the Northwest Pacific in 2007 are analyzed. The results are as follows: (1) The average error of tropi cal cyclone position is less than 25 km. (2) Error of intensity forecasts is sim ilar to that in past years with an average of 3～7m?s-1 and 5～11m?s -1 for 24h and 48h forecasts, respectively. (3) Average error of synthetic track forecasts is 129.8 km (24h) and 215.0 km (48h). Although numerical models are still not as good as synthe tic forecasters in track prediction, the super ensemble method of multiple numer ical models demonstrates positive skill compared with synt hetic forecasts. Statistical methods are still widely used in intensity predicti on.
Positioning and forecast errors of tropical cyclones over the Northwest Pacific in 2007 are analyzed. The results are as follows: (1) The average error of tropi cal cyclone position is less than 25 km. (2) Error of intensity forecasts is sim ilar to that in past years with an average of 3～7m?s-1 and 5～11m?s -1 for 24h and 48h forecasts, respectively. (3) Average error of synthetic track forecasts is 129.8 km (24h) and 215.0 km (48h). Although numerical models are still not as good as synthe tic forecasters in track prediction, the super ensemble method of multiple numer ical models demonstrates positive skill compared with synt hetic forecasts. Statistical methods are still widely used in intensity predicti on.
2009, 35(2):106-110.
DOI: 10.7519/j.issn.1000-0526.2009.2.016
Abstract:
At present the metrological standard instrument and methods are not applicable t o ground meteorological station apparatus. To solve these problems, an autotes t system of ground meteorological station are designed. The characteristic of the system is that the capability autotest of ground meteorological station sensor and data collector is divided. Autotest system of ground meteorologica l station sensors, like temperature, humidity, atmospheric pressure, wind direct ion, wind speed and precipitation sensors, adopt multichannel design, so many sensors can be autotested at the same time and test result provided automatica lly. Autotest system of data collector can make capability autotest for diff e rent data collector system in each ground meteorological station. The designed a utotest system of ground meteorological station enhances the test efficiency o f ground meteorological instruments and ensures the accurate and reliability of ground meteorological observational data.
At present the metrological standard instrument and methods are not applicable t o ground meteorological station apparatus. To solve these problems, an autotes t system of ground meteorological station are designed. The characteristic of the system is that the capability autotest of ground meteorological station sensor and data collector is divided. Autotest system of ground meteorologica l station sensors, like temperature, humidity, atmospheric pressure, wind direct ion, wind speed and precipitation sensors, adopt multichannel design, so many sensors can be autotested at the same time and test result provided automatica lly. Autotest system of data collector can make capability autotest for diff e rent data collector system in each ground meteorological station. The designed a utotest system of ground meteorological station enhances the test efficiency o f ground meteorological instruments and ensures the accurate and reliability of ground meteorological observational data.
2009, 35(2):111-118.
DOI: 10.7519/j.issn.1000-0526.2009.2.017
Abstract:
The features of changes for agroclimatic elements and agroclimatic m atching types in Yunnan were investigated. On the basis of historical climatic d ata from observed stations, orthogonal expansion method was used to extract stap le components from 17 climatic factors for three periods amid anniversary denoti ng local agroclimatic features. And hierarchical cluster method was employed t o divide agroclimatic matching classes of Yunnan. As the results of this resea rch, the principal changes of agroclimatic elements and annual agroclimatic types were summarized by 7 principal components independent of each other and 6 annual agroclimatic types. The research shows that there was a trend of climate warming during the principa l season of Yunnan agriculture among the recent 54 years and it has been reinfor ced since 1990s. On the other hand, the annual changes of precipitation and suns hine duration were more conspicuous than airtemperature; the amplitude of sunshine duration was at least equivalent to one of precipitation; the drought strength in spring was decreasing; successive rain ing and shortened sunshine duration have an aggravated trend. With the reinforce ment of climate warming since 1995, the precipitation in summer has a decreasing trend whilst the amplitude of sunshine duration is large. From 1954-2007, only the minority of years has the agroclimatic type analogous to their previous ye ars. Moreover, there are only 2 agroclimatic types mainly affecting Yunnan reg ion since 1995. And the dominating agroclimatic type arisen since the end of l ast century did not occur in 1950s, 1960s and 1970s, which has distinctive clima tic traits. The effects of these climate changes on agriculture in Yunnan are wo rth paying close attention. This research is very helpful to evaluating climatic influence, predicting agricultural production and undertaking meteorological se rvices.
The features of changes for agroclimatic elements and agroclimatic m atching types in Yunnan were investigated. On the basis of historical climatic d ata from observed stations, orthogonal expansion method was used to extract stap le components from 17 climatic factors for three periods amid anniversary denoti ng local agroclimatic features. And hierarchical cluster method was employed t o divide agroclimatic matching classes of Yunnan. As the results of this resea rch, the principal changes of agroclimatic elements and annual agroclimatic types were summarized by 7 principal components independent of each other and 6 annual agroclimatic types. The research shows that there was a trend of climate warming during the principa l season of Yunnan agriculture among the recent 54 years and it has been reinfor ced since 1990s. On the other hand, the annual changes of precipitation and suns hine duration were more conspicuous than airtemperature; the amplitude of sunshine duration was at least equivalent to one of precipitation; the drought strength in spring was decreasing; successive rain ing and shortened sunshine duration have an aggravated trend. With the reinforce ment of climate warming since 1995, the precipitation in summer has a decreasing trend whilst the amplitude of sunshine duration is large. From 1954-2007, only the minority of years has the agroclimatic type analogous to their previous ye ars. Moreover, there are only 2 agroclimatic types mainly affecting Yunnan reg ion since 1995. And the dominating agroclimatic type arisen since the end of l ast century did not occur in 1950s, 1960s and 1970s, which has distinctive clima tic traits. The effects of these climate changes on agriculture in Yunnan are wo rth paying close attention. This research is very helpful to evaluating climatic influence, predicting agricultural production and undertaking meteorological se rvices.
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ISSN:1000-0526 CN:11-2282/P